Begin PARAL 1.4              Larry Hoppis                Elinel Consulting

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The following HP48 program contains general 1% resistor utilities for 
electronics technicians and hobbyists. The main program 'RPAR' will 
find all combinations of parallel 1% resistors to obtain the desired 
value within a given accuracy.  This is useful in case you don't have
the value you need on hand, but also because the exact value you want
may not be a standard off-the-shelf value.

:USAGE:


RPAR:   Put the value of the resistance you want in level 1 of the stack 
        and press RPAR. RPAR presents a list of standard 1% resistance 
        values which when paralleled will yield the desired value. The 
        accuracy of each combination is also displayed. The required 
        accuracy is specified by the variable 'ACCU'. Pressing ACCU will 
        bring the accuracy value to the stack. Left-shift ACCU will 
        store the value on the stack into ACCU. 

        RPAR displays 9 solutions at a time using the small graphics 
        font. Pressing '+' (or any other key) will advance to the next 
        page. Pressing '-' will return to the previous page.  Pressing 
        the backarrow key (unshifted DROP) will exit the program and 
        return the original value to the stack. 
      
NXT:    Given any value in level 1, will return the first standard 1 % 
        value which occurs above that value.                 

PRV:    Given any value in level 1, will return the first standard 1 % 
        value which occurs below that value.                  

->PAR:  Takes any two values in levels 1 and 2 and returns the parallel 
        combination of those two values to level 1. 

DSP:    Takes any value in level 1 decimal adjusts it for k or M 
        scientific notation and returns it as a padded string to level one. 

->BIN:  Takes any resistance value in level 1 and returns a bin number n 
        such that when n is a positive integer it represents the nth 
        calculated 1% resistance value (starting at 1 ohm). For example 
        if there were a numbered drawer for every 1% resistor value
        ->BIN would return the drawer number for a given value. 

->VAL:  Inverse of ->BIN. Takes any bin value in level 1 and returns the 
        value that would occupy that bin.  If the input is an integer, 
        an exact calculated 1% value will be generated.  
        
  NOTE:   Both ->BIN and ->VAL work with the _calculated_ 1% values 
          which must be rounded to 3 significant places to correspond 
          with standard 1% values. 

TONE:   Signal sound.  You can copy this to your home directory, then
        purge it; it is useful in other programs too.

THEORY: RPAR uses an equation I derived with the HP48 from a list of 
        valid 1% values.  This list was also created on the '48 using 
        the formula 

                INV(96)
        X = X*10        for all values between 1 ohm and 1 G ohm

      
                                        0.0239852613838*X
        The HP48 found  0.976300098965*e                  


This Equation and its inverse form the basis of ->BIN and ->VAL.  
Similiar equations could be derived for other resistor series such as 5% 
or 10 %.  Utilizing these equations RPAR is accurate to at least 4 
decimal places for all values from 1 ohm to 9.76E499 ohms - now that's a 
big resistor! *:-). 

COPYRIGHT

PARAL is copyrighted and may not be distributed for money under any 
circumstance except in the case of a user group which may recoup a 
small duplication fee.  PARAL may be freely copied and distributed as 
long as this original documentation remains with it.  Please use and 
enjoy PARAL and contact me with any suggestions or comments.

   Larry L. Hoppis     |  quality!hoppis@ucscc.UCSC.edu   |  Love that '48!!
   240 Azalea Ave.
   Ben Lomond  CA
   95005 408-336-3651